Fluid Dynamics in Earth and Planetary Sciences (FDEPS) 4th FDEPS workshop Nov 11 - Nov 15, 2002 Graduate School of Mathematical Sciences, University of Tokyo
Atmospheric poleward energy fluxes, turbulent cascades, and the
efficiency of the atmospheric heat engine.
Held, Isaac M. (GFDL/Princeton University)
A theory for the poleward energy flux in the atmosphere is outlined based on diffusivities obtained from models of homogeneous baroclinic turbulence.
Developments in the theory of homogeneous baroclnic turbulence are described, building on the picture described in Held and Larichev (Journal of the Atmospheric Sciences, 53, 946-952). The central questions in these theories are 1) how is the inverse energy cascade halted? and 2) how is the diffusivity for potential vorticity controlled in the resulting flow? An attempt is then made to reconcile these theories with the fact that the observed energy spectra in the atmosphere are not those expected of a flow with a well-developed inverse cascade. Problems in extending these ideas to moist atmospheres are described. The relationship between these diffusive theories and estimates of the "efficiency" of the atmosphere is discussed, touching on the recent paper of Barry, Craig, and Thuburn (Nature, 415, 774 - 777, 14 Feb 2002). We then discuss whether or not it is is useful, in the presence of moisture, to think of the atmosphere as a "heat engine' or as a "dehumidifier", following the recent work of Pauluis and Held (Journal of the Atmospheric Sciences, 59, 125-139).